Acceleration sensors typically use a proof mass to convert acceleration into force through Newton's law F=MA. In function, the accelerometer typically measures the force as an analog of acceleration.
The proof mass in the accelerometer is typically planar in form and has a flexure suspension permitting a single degree of motional freedom. In most accelerometers, this planar proof mass is surrounded by planar features (typically above and below the proof mass) known as “damping plates” or “cover plates”, which serve to limit the permissible proof mass's travel and provide damping through squeeze-film-gas effects—see QFlex, resonating beam accelerometer (RBA), and microelectromechanical systems (MEMS) accelerometer.
The proof mass and damping plates are often made from insulating materials (e.g., fused silica, amorphous quartz, crystalline quartz, Pyrex, glass) that, when exposed to a suitable environment, can trap charge. Charge accumulated between the proof mass and damping plates results in an attraction or a repulsion force, which is indistinguishable from the Newtonian force and therefore results in an error in the accelerometer's output.
A prior-art solution to this problem is to apply a conductive metal film to the insulator surfaces to dissipate the accrued charge to electrical ground. In many cases, use of metal for this purpose is undesirable due to issues with metal stress, thickness, thermal expansion coefficient, and thermal conductivity, which lead to undesired output errors.